The present invention relates to a cementitious facing composition for bonding to a base material, and more particularly, to a facing composition using an aqueous emulsion of a polymer bonding agent as a wetting agent.
There is often a need to apply a facing to a base material, for instance, individual bricks or concrete blocks, or existing masonry and concrete walls, floors and slabs or the like or gypsum board in order to give a finished appearance to the base material. It is desirable to have a facing which has the appearance of fine grained concrete and provides a water-resistant, wear-resistant, resilient, tough and uniformly colored surface which will maintain its appearance with minimum maintenance. It has been a recurring problem to find a facing material which would economically fulfill all of these requirements and could be easily made and applied in the field.
In the past, many base materials have simply been coated with various mixtures of Portland cement and sand or just Portland cement to accomplish this end. This is commonly done for structures made of brick or concrete block. Whether this coating is applied directly to the brick or block before assembly or to the assembled structure, the facing has many disadvantages. It is usually not water-resistant so that some separate waterproofing composition like paint or sealer must be applied. Such facings are also usually brittle so that they may be damaged when hit. If individual blocks are faced before assembly, the facing can easily be chipped off the block during shipping or handling.
In those applications where it is important to have a surface which will resist damage from impacts, various kinds of plastic coatings have been used for the individual building bricks or blocks or the assembled structure. These materials have the disadvantage of being difficult to maintain, especially when it is desired to provide a uniform and long lasting color to the facing.
Obtaining a satisfactory bond between the facing and base material has also been a recurring problem. In order to overcome the problems of bonding the facing to the base material, it has been suggested to use bonding agents directly between the facing and the base such as the reemulsifying, polyvinyl acetate adhesive composition disclosed in U.S. Pat. No. 2,760,885 to Larsen. Although these types of bonding agents provide an improved bond between the facing and the base material, the facing itself remains brittle, water absorbent and weather sensitive.
To overcome some of the disadvantages of cementitious facing, in some applications, individual pieces of hard weather and water resistant material such as ceramic tile have been bonded to the base material. Although such tile is water-proof and retains its appearance, maintaining the tile bonded to the base material is difficult and the tiles themselves are brittle.
There is a particularly difficult problem of providing a proper coating to a concrete slab such as would be used for a floor, sidewalk, driveway or patio. Such slabs are conventionally made with a substrate composed of cement, light aggregate like sand and heavy aggregate like stone and a surface composed of cement and light aggregate sand. Because such slabs are exposed to a wide range of weather conditions and sometimes very heavy loading, it is difficult to maintain the surface intact. The surface is also easily discolored because it is porous.
Concrete floors, such as those used in many industrial environments, are noted for being uncomfortable to stand or walk on for long periods of time. People who must walk on hard concrete floors soon develop pains and aches in their legs and feet muscles and joints. Carpeting or wooden flooring or various kinds of cushioned tile have been used over the concrete to provide cushioning. Although carpet, wood or tile floors can be beautiful, they are expensive to install and clean. Providing cushioning in the surface layer of a concrete floor would provide the cushioning of more expensive floors and still maintain the durability, appearance and easy cleaning of concrete.
In the past, various ingredients have been used as additives to concrete as, for example, strengtheners or as setting accelerators or retardants. A variety of vinyl polymers have been used to strengthen concrete and to improve its resistance to chemicals. See for example U.S. Pat. No. 3,850,651 where vinyl polymers or copolymers have been incorporated into cement compositions and cured at elevated temperatures.
Even in view of all the work that has been done with cement, there is still a need for a facing composition that can be used to cover a variety of base materials and provide a pleasing appearance which is water-resistant, wear-resistant, resilient, tough, uniformly colored and relatively maintenance free. It is also desirable that such a facing material have the versatility to be applied either directly to individual brick or block or to the assembled masonry or concrete walls, floor or slab as a whole.